The mercury was not added by the manufacturer, but by a third party, DHS said.

The 47-year-old woman's son told KCRA his mother has been in the hospital since July when she first showed up at the emergency room reporting numbness in her hands and face, slurred speech and trouble walking. Her condition deteriorated over the next few weeks.

Sacramento County Public Health Officer Dr. Olivia Kasirye said mercury is added to these products because it stops the production of melanin in the skin, which helps reduce the appearance of age spots, lightens the skin and fades freckles. However, the pigment-busting ingredient can have damaging side effects.

"It can reach high levels in the blood and it can also cross into the brain and once it crosses into the brain even if you go to the hospital the medication we have cannot pull it out,” Kasirye told KCRA.

According to the World Health Organization, skin lightening creams containing mercury is commonly used in certain African, Asian, European and North American countries for its skin lightening abilities. However, the mercury-laced products are banned by the European Union and in many African nations. The U.S. Food and Drug Administration permits the use of mercury compounds only in "eye area" products, limited to 65 parts per million (0.0065 percent).

These illegal mercury-tainted creams are commonly sold in small stores, swap meets or online.

The agency noted that in California alone, more than 60 cases of poisoning linked to foreign, unlabeled or homemade skin creams have been reported over the last nine years. However, this is first known case of mercury poisoning "of this type" linked to a skin cream in the U.S., DHS said.

“Sacramento County Public Health urges the community to immediately stop using similar skin creams imported from Mexico due to the risk of contamination with methylmercury,” said Sacramento County Public Health Officer Dr. Olivia Kasirye in a news release. “Methylmercury is extremely dangerous to adults and children.”